The invention concerns a system for pumping a liquid and a corresponding amount of vapor, which system includes a tank, a pump and a volumeter which are all interconnected with pipes for the displacement of liquid from one tank to another, and which system has an air pump for pumping a corresponding amount of vapor in the opposite direction.
Similar systems are used not only in pump stations such as gasoline pump stations, but also in pump stations in industrial complexes where more or less noxious, or maybe volatile, liquids need to be pumped from one storage tank to another without causing any vapor which has formed, or is being formed in the collection tank, from being released into the environment by way of the intake. Not only are such vapors pollutants but, because they are derived from the liquid, the loss of such vapors represents also a waste of the liquid. Obviously, both the environmental pollution and the waste are unacceptable.
To prevent these problems, known systems have been developed which make use of two--generally--electrical pumps, whereby one pump in installed in the pipe for the liquid which in general contains also a volumeter, and the other pump is installed in the air pipe. When the pump for the liquid is turned on the air pump is also activated, as a result of which, during the operation of the system, the volume of liquid displaced over a certain period of time will correspond to the displaced volume of air. The simultaneous activation of both pumps occurs in the known system by means of switches, e.g., electrical switches, which must be installed on each pump.
The disadvantage of the known system is that, although the volume of the liquid displaced during stationary operation of the system corresponds to the volume of displaced air, when the pumping process is examined in its entirety, the volume of the displaced liquid does not correspond with sufficient accuracy to the volume of displaced air.